With the widespread application of blockchain technology, its communication security has become a core issue for research, especially in the scenario of financial transactions. Due to the semi-trustworthiness of the broadcast center, broadcast encrypted messages may be at risk of tampering. This leads to the risk that broadcast data can be revoked and untrusted, and causes disorder in the system. This paper employs the SM2 encryption algorithm and blockchain technology to devise a trustworthy and tamper-resistant broadcast encryption scheme. To enhance the interaction efficiency of asymmetric group key agreement protocol and address the inherent collusion attack, the BLS short signature technology is used in this paper. We also design a group anonymous authentication and designated receiver encryption mechanism from the asymmetric group key agreement protocol. The protocol analysis indicates that the devised protocol possesses session key unforgeability and resilience against collusion attacks. Innovatively, the security of broadcast encryption is improved, and the efficiency and reliability of communication are ensured by combining the blockchain technology and SM2 public key encryption algorithm.